A gas turbine, such as one used for generating power, includes, as its main components, a compressor, a combustor, and a turbine. Many gas turbines have a plurality of combustors, and the combustors included in the gas turbine are arranged in a circle in a combustor casing. Air compressed by the compressor is mixed with fuel supplied into the combustors, and is combusted. Such combustion takes place in each of the combustors to generate high temperature combustion gas. The combustion gas, produced by the combustion, is supplied to the turbine to drive the turbine in rotation.
FIG. 8 indicates an exemplary structure of a combustion burner included in a combustor of a conventional gas turbine. As shown in FIG. 8, this combustion burner 100A is arranged in plurality (in FIG. 8, only one is depicted), surrounding a pilot combustion burner 200. A pilot combustion nozzle, not shown, is installed in the pilot combustion burner 200. The combustion burner 100A and the pilot combustion burner 200 are arranged in a combustion liner of the gas turbine. The combustion burner 100A includes, as main component thereof, a fuel nozzle 110, a burner tube 120, and swirler vanes (swirler vane) 130 (Patent Documents 1 and 2).
The burner tube 120 is arranged along the same axis as the fuel nozzle 110, surrounding the fuel nozzle 110, to provide a ring-like air passage 111 between the external circumferential surface of the fuel nozzle 110 and the inner circumferential surface of the burner tube 120. Compressed air A flows through the air passage 111 from upstream (from the left-hand side in FIG. 8) to downstream of the air passage 111 (toward the right-hand side in FIG. 8). The swirler vanes 130 are arranged in a plurality of positions along the circumferential direction of the fuel nozzle 110, each extending in the axial direction of the fuel nozzle 110. A clearance (gap) 121 is kept between the tip (tip) of the external circumference of each of the swirler vanes 130 and the inner circumferential surface of the burner tube 120, generating a leaking air flow that flows around a vane pressure surface of each of the swirler vanes 130 to a vane suction surface thereof. This leaking flow interferes with the compressed air A to generate a vortical air flow. By way of such a vortical air flow, the compressed air A is effectively mixed with vaporized and atomized fuel F injected from a point near the tip of the fuel nozzle 110 to the vane surface. In this manner, even distribution of the fuel is promoted. The reference numeral 131 in FIG. 8 indicates a clearance setting rib.
The gas turbine uses not only a gas fuel but also a liquid fuel as a fuel. Conventionally, when a liquid fuel is used, the liquid fuel is injected through a liquid fuel injecting hole toward the flow of the compressed air. In this manner, the injected liquid fuel is sheared by the compressed air flow, and becomes atomized and mixed with air. The liquid fuel that is atomized and mixed with air is then combusted.
Examples of liquid fuels include, the bunker A, light oil, and dimethyl ether that are so-called oil fuel.
When a liquid fuel is used in the conventional combustion burner 100A, the liquid fuel is supplied from the point near the tip of the fuel nozzle 110, and each of the swirler vanes 130 gives a swirling force to the compressed air A that is flowing through the air passage 111 to obtain a swirling air flow a. The kinetic momentum of the swirler air is used to atomize the liquid fuel, and to reduce NOx and suppress soot.
However, the conventional combustion burner 100A, such as the one shown in FIG. 8, has been limited in its capability to atomize the liquid fuel. Furthermore, it has been extremely difficult to make the fuel density uniform in the fuel nozzle 110.
To prevent these problems, a combustion burner has been suggested to promote atomization and to make the fuel density uniform. FIG. 9 is a schematic of an exemplary structure of another conventional combustion burner. FIG. 10 is a perspective view of the fuel nozzle included in the conventional combustion burner. As shown in FIGS. 9 and 10, this conventional combustion burner 100B supplies a liquid fuel LF through liquid fuel injecting holes 133A arranged on the surface of the fuel nozzle 110. The liquid fuel LF, injected through the liquid fuel injecting holes 133A, is injected toward the vane pressure surface 132a of the swirler vane 130. On the vane pressure surface 132a, the liquid fuel LF spreads out into a thin film. The liquid fuel LF that is spread into a thin film is sheared by a high-speed air flow, to become atomized and vaporized. In this manner, atomization is promoted, and uniform fuel density is achieved (Patent Document 3).
[Patent Document 1] Japanese Patent Application Laid-open No. H11-14055
[Patent Document 2] Japanese Patent Application Laid-open No. 2004-12039
[Patent Document 3] Japanese Patent Application Laid-open No. 2006-336997